Bellows-enabled bleed valve

ABSTRACT

A bleed valve for use in a gas turbine engine of an aircraft includes a high-pressure cavity coupled to a valve terminal, which is itself coupled to a cap, which cap includes a valve seat configured to be sealed by a tube that serves as the valve gate. The tube is operably coupled to a movable end of a bellows, which is positioned within the high-pressure cavity. The opening and closing of the valve is controlled by the movement of the bellows within the high-pressure cavity, and, in turn, the movement of the tube towards the valve seat, with the valve closing as the bellows compresses.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and is a continuation-in-part ofU.S. patent application Ser. No. 16/149,860, filed Oct. 2, 2018, theentirety of which is incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present invention relates to bleed valves used in the gas turbineengines of aircraft, and, in particular, to such bleed valves having abellows for regulating the flow of gases, including air, from within theengine through the valve, and out into the surrounding environment.

BACKGROUND

Valves are well-known to be useful for regulating the flow of fluids.Moreover, compressible and expandable bellows structures have been knownto be useful for controlling highly pressurized fluids to enable thefacilitated regulation of such valves. For example, valves can beconfigured to be opened and closed through the use of bellows, which canexpand and/or compress, based on the pressure of certain fluidscontained within, and/or surrounding, the bellows.

In the context of gas turbine engines, it is also well known that valvesmay be necessary to bleed air away from the compressor section of theengine. For example, bleed valves may be helpful or even necessaryduring the start-up of the engine, in order to reduce the load needed todrive the compressor associated therewith. Bleed valves may also be usedto ensure safe operating conditions in other situations during theoperation of the engine, and, in turn, the aircraft.

For example, the compressor sections of gas turbine engines may beunstable, in that the airfoils can stall when the airflow is too low. Inthat situation, stall cells may form and rotate inside the compressorsection, thereby compromising the performance and efficiency of thecompressor, and, in turn, the engine. If the pressure rises sharply,there may be a risk that the entire engine could surge, thus resultingin flames being emitted out of the engine fan. In that situation, theengine would need to be shut down and restarted. This is a verydifficult proposition if the surge occurs while the aircraft is inflight. Bleed valves may help to avoid such consequences by allowing airand other gases to escape, and by increasing the flow of air through thecompressor.

Bleed valves may also be needed in other situations such as, forexample, during a quick acceleration from idle to full power. In thatsituation, the front stages of a compressor section may be pumping airat a rate of flow and/or pressure that is much larger than the backstages of a compressor section may be able to accept. This mismatch inairflow and pressure throughout the entire compressor section may causethe compressor to stall. One or more bleed valve(s) may be used duringthese conditions to allow air from the front stages of the compressorsection to escape. The valve(s) may then be closed when the engine againreaches a steady operating condition.

Bleed valves for these types of uses have been described in manydifferent configurations. As aircraft engine technology continues toimprove, however, there continues to be a need for bleed valves that arecapable of withstanding higher pressures and temperatures. For instance,current bleed valve technologies often utilize carbon seals as a dynamicor sliding sealing mechanism. Carbon seals present their owndifficulties, however. For example, carbon seals are known to havetemperature limitations, and high temperature applications can leadconventional carbon seals to fail. In addition, the use of carbon sealsresults in other problems or requirements; they can wear and/or degradequickly, and thus they may require regular replacement or substantialmaintenance. By way of example, in certain bleed valve technologies nowin use, while many of the major components of the bleed valve may have arelatively long lifespan, the carbon seals within such a bleed valve mayneed to be regularly replaced in order to enable the bleed valve tofulfill that longer lifespan. Accordingly, certain advantages may berealized through a bleed valve design that completely eliminates theneed for dynamic sliding seals made of carbon.

SUMMARY OF THE INVENTION

In one aspect of the present embodiments, a bleed valve is described foruse in a gas turbine engine of an aircraft. The bleed valve comprises ahigh-pressure cavity having an interior surface, an interior volume, anexterior surface, a first end and a second end opposite the first end;and a valve housing having an exterior surface, a first end, a secondend opposite the first end, and a plurality of apertures, said secondend of said high-pressure cavity being coupled to said first end of saidvalve housing. The bleed valve further comprises a bellows foralternatively capturing and releasing one or more pressurized fluids.The bellows has an interior surface, an interior volume, an exteriorsurface, a first movable end and a second fixed end opposite the firstmovable end. The second fixed end of the bellows is operably coupled toone of the interior surface of the high-pressure cavity and the exteriorsurface of the valve housing, at a position substantially adjacent thesecond end of the high-pressure cavity.

The bleed valve further includes a shaft having a first end and a secondend opposite the first end, where the first end of the shaft is operablycoupled to the first movable end of the bellows, and the second end ofthe shaft is coupled to a system poppet configured to seal a valve seatsubstantially adjacent the second end of the valve housing. The shaft isalso sealed relative to the interior surface of the bellows, to precludethe undesired entry and release of any of the pressurized fluidstherefrom.

In addition, the bleed valve further comprises (i) at least one cavityair port configured to inject a first of the pressurized fluids into theinterior volume of the high-pressure cavity about the exterior surfaceof the bellows, so as to exert a first pressure against the exteriorsurface of the bellows, thereby compressing the bellows; and (ii) atleast one servo air port configured to inject a second of thepressurized fluids directly into the interior volume of the bellows, soas to exert a second pressure against the interior surface of thebellows, thereby expanding the bellows.

In some embodiments of the bleed valve described herein, the injectionof the first and second of the one or more pressurized fluids via the atleast one cavity air port and the servo air port, respectively, iscollectively configured to be controllable by one of (a) a pilot of theaircraft, (b) an onboard flight computer, or (c) by other means.

In some embodiments of the bleed valve described herein, the at leastone cavity air port is encased within the valve housing.

In some embodiments of the bleed valve described herein, the servo airport is encased within the valve housing.

In some embodiments of the bleed valve described herein, the bellows hasrectangular weld beads, such that when the bellows is compressed intoits fully nested position, the rectangular weld beads stack on top ofone another to form a solid, self-supporting cylindrical stack.

In some embodiments of the bleed valve described herein, the meaneffective area of the bellows is larger than the mean effective area ofthe system poppet.

In some embodiments of the bleed valve described herein, the firstmovable end of the bellows is rigidly coupled and hermetically sealed tothe shaft.

In some embodiments of the bleed valve described herein, the fixed endof the bellows is hermetically sealed against the release of the one ormore pressurized fluids by a posterior surface of the system poppet.

In some embodiments of the bleed valve described herein, the rigidcoupling and hermetic sealing of the first movable end of the bellowsand the shaft is accomplished through welding.

In some embodiments of the bleed valve described herein, the rigidcoupling and hermetic sealing of the first movable end of the bellowsand the shaft is accomplished through laser welding.

In some embodiments of the bleed valve described herein, the bleed valvefurther comprises an over-travel element, wherein the bellows isconfigured to fully nest after the poppet has fully seated.

In some embodiments of the bleed valve described herein, the over-travelelement comprises one or more flexure elements that are coupled to thefirst movable end of the bellows, thereby enabling the bellows to fullynest upon application of the first pressure, when the first pressureexceeds a threshold pressure required to enable the system poppet toseal against the valve seat.

In some embodiments of the bleed valve described herein, the shaftcomprises a single, solid, integrated assembly without any internalcavities therewithin.

In some embodiments of the bleed valve described herein, the shaftcomprises an internal shaft cavity, and the first end of the shaft isoperably coupled to the first movable end of said bellows via a shaftextension having a first end and a second end opposite the first end. Inthese embodiments, the over-travel element may comprise a springpositioned inside the internal shaft cavity, with one end of the springbearing against the second end of the shaft extension, to bias thesystem poppet into a position open and apart from the valve seat.

In some embodiments of the bleed valve described herein, the bleed valveis configured to be positioned within the compressor stage of the gasturbine engine.

In some embodiments of the bleed valve described herein, the bleed valveis configured to be positioned within the turbine stage of the gasturbine engine.

In some embodiments of the bleed valve described herein, the bleed valveis configured to be positioned within the combustor stage of the gasturbine engine.

In some embodiments of the bleed valve described herein, the bleed valveis configured, when in its closed position in which the system poppet issealed against the valve seat, to be positioned such that a pressurizedgas flowing through the compressor stage of the gas turbine engine isprevented from flowing through the valve seat.

In some embodiments of the bleed valve described herein, the bellows isconfigured to be in a compressed state when the valve is closed.

In some embodiments of the bleed valve described herein, the bellows isconfigured to be capable of further compression to a nested state whenthe valve is closed.

In some embodiments of the bleed valve described herein, the bleed valvefurther comprises an integrated filtration unit to prevent one or morecontaminants from entering the high-pressure cavity.

In some embodiments of the bleed valve described herein, the integratedfiltration unit comprises one or more filter discs positioned betweenthe valve housing and the high-pressure cavity, within one of the one ormore cavity air ports and the servo air port.

In some embodiments of the bleed valve described herein, the bleed valvefurther comprises one or more sealing elements in the form of a seriesof welded joints at the first movable end and the second fixed end ofthe bellows.

In some embodiments of the bleed valve described herein, the bleed valvefurther comprises one or more sealing elements in the form of an annularcontact seal formed between a posterior surface of the system poppet andan interior surface of the valve housing.

In some embodiments of the bleed valve described herein, the bleed valvefurther comprises one or more sealing elements in the form of an annularsealing ring positioned between the second end of the high-pressurecavity and the first end of the valve housing.

In some embodiments of the bleed valve described herein, the bleed valvefurther comprises an end cap that is rigidly coupled and hermeticallysealed to said first movable end of the bellows and said shaft.

In yet another example of the present embodiments, a bleed valve isdescribed for use in a gas turbine engine of an aircraft. The bleedvalve comprises housing elements, including (1) a high-pressure cavityhaving an interior surface, an interior volume, a first end and a secondend opposite the first end; (2) a valve terminal having an exteriorsurface, a first end, a second end opposite the first end, and one ormore apertures, the second end of the high-pressure cavity being coupledto the first end of the valve terminal; and (3) a cap having a first endand one or more apertures, said second end of said valve terminal beingcoupled to said first end of said cap.

The bleed valve further comprises a bellows for alternatively capturingand releasing one or more pressurized fluids, the bellows having aninterior surface, an interior volume, an exterior surface, a firstmovable end and a second fixed end opposite the first movable end. Thesecond fixed end of the bellows is operably coupled to one of theinterior surfaces of the high-pressure cavity and the exterior surfaceof the valve terminal, at a position substantially adjacent the secondend of the high-pressure cavity. The valve also comprises a sealing tubehaving a first end and a second end opposite the first end, where thefirst end of the sealing tube is operably coupled to the first movableend of the bellows, the second end of the sealing tube being configuredto cooperate with and seal a valve seat located on the cap. Notably,unlike the first embodiment described above beginning at Paragraph[0008], the present embodiment of the bleed valve does not incorporateor utilize a shaft that is operably coupled to a system poppet that isconfigured to seal a valve seat. Rather, in this present embodiment, thesealing tube extends from the first, movable end of the bellows all theway to the valve terminal, where the second end of the sealing tube isconfigured to cooperate with the valve seat located on the cap.

The bellows is configured to expand and compress based upon theorientation of one or more pressurized fluids into the bellows andsurrounding the bellows, respectively, and the bleed valve is configuredto be self-compensating, in that when the bleed valve is in its closedconfiguration, the sealing tube is oriented to be effectively sealedagainst the valve seat, with the bellows in its compressed position.

In some embodiments of the bleed valve described herein, the injectionof the one or more pressurized fluids is collectively configured to becontrollable by one of (a) a pilot of said aircraft, (b) an onboardflight computer, or (c) by other means.

In some embodiments of the bleed valve described herein, a servo airport is encased within the valve housing.

In some embodiments of the bleed valve described herein, the bellows hasrectangular weld beads, such that when the bellows is compressed intoits fully nested position, the rectangular weld beads stack on top ofone another to form a solid, self-supporting cylindrical stack.

In some embodiments of the bleed valve described herein, the meaneffective area of the bellows is larger than the mean effective area ofthe sealing tube.

In some embodiments of the bleed valve described herein, the firstmovable end of the bellows is rigidly coupled and hermetically sealed tothe sealing tube.

In some embodiments of the bleed valve described herein, the rigidcoupling and hermetic sealing of the first movable end of the bellowsand the sealing tube is accomplished through welding.

In some embodiments of the bleed valve described herein, the rigidcoupling and hermetic sealing of the first movable end of the bellowsand the sealing tube is accomplished through laser welding.

In some embodiments of the bleed valve described herein, the bleed valveis configured to be positioned within the compressor stage of the gasturbine engine.

In some embodiments of the bleed valve described herein, the bleed valveis configured to be positioned within the turbine stage of the gasturbine engine.

In some embodiments of the bleed valve described herein, the bleed valveis configured to be positioned within the combustor stage of the gasturbine engine.

In some embodiments of the bleed valve described herein, the bleed valveis configured, when in its closed position in which the sealing tube issealed against the valve seat, to be positioned such that a pressurizedgas flowing through the compressor stage of the gas turbine engine isprevented from flowing through the valve seat.

In some embodiments of the bleed valve described herein, the bellows isconfigured to be capable of further compression to a nested state whenthe valve is closed.

In some embodiments of the bleed valve described herein, the bleed valvefurther comprises an integrated filtration unit to prevent one or morecontaminants from entering the high-pressure cavity.

In some embodiments of the bleed valve described herein, the integratedfiltration unit comprises an air filter positioned at the bottom of thehigh-pressure cavity.

These and other embodiments of the invention will be apparent in lightof the present specification, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, cross-sectional view of an example gas turbineengine.

FIG. 2A is an elevated cross-sectional view of a bleed valvecorresponding to a first embodiment of the present invention, in whichthe valve is akin to a globe valve having a disc-shaped system poppetthat cooperates with a circular valve seat, where the valve is shown inits open position.

FIG. 2B is an elevated cross-sectional view of the bleed valve of FIG.2A, with the valve again shown in its open position, in which the valveis shown in one potential environment in which the valve may be used,i.e., mounted onto the casing of the compressor section of a gas turbineengine.

FIG. 3 is an elevated cross-sectional view of the bleed valve of FIGS.2A-2B, with the valve shown in its closed position in which the bellowsis partially compressed, such that the system poppet has just beensealed against the valve seat.

FIG. 4 is an elevated cross-sectional view of the bleed valve of FIGS.2A-2B, with the valve shown in a position in which the bellows is fullycompressed into a nested position, such that the system poppet isforcibly sealed against the valve seat.

FIG. 5 is a cross-sectional view of the bleed valve of FIGS. 2A-2B, withthe valve shown in a position in which the bellows has been forced toexpand again to its original open position.

FIG. 6 is an elevated cross-sectional view of a bleed valvecorresponding to a second embodiment, in which the shaft that connectsthe movable end cap of the bellows to the system poppet comprises asingle, solid, integrated assembly without any internal cavitiestherewithin, also with the bleed valve in its open position.

FIG. 7 is an elevated cross-sectional view of a bleed valvecorresponding to a third embodiment of the present invention, in whichthe valve is more akin to a gate valve having a tubular gate or wedgethat actuates to seal the valve, where the valve is shown in its openposition.

FIG. 8 is an elevated cross-sectional view of the bleed valve of FIG. 7,with the valve shown in its closed position in which the bellows ispartially compressed, such that the tubular gate or wedge has just beensealed against the valve seat.

FIG. 9 is an elevated cross-sectional view of the bleed valve of FIG. 7,with the valve shown in a position in which the bellows is fullycompressed into a nested position, such that the tubular gate or wedgeis substantially sealed against the valve seat.

FIG. 10A is a cross-sectional perspective view of the bleed valve ofFIG. 7, viewed from slightly above, with the valve shown in its openposition, in which the bellows is in its expanded position.

FIG. 10B is a cross-sectional perspective view of the bleed valve ofFIG. 7, viewed from slightly below, with the valve shown in its openposition, in which the bellows is in its expanded position.

FIG. 11A is a cross-sectional perspective view of the bleed valve ofFIG. 8, viewed from slightly above, with the valve shown in its closedposition in which the bellows is partially compressed, such that thetubular gate or wedge has just been sealed against the valve seat.

FIG. 11B is a cross-sectional perspective view of the bleed valve ofFIG. 8, viewed from slightly below, with the valve shown in its closedposition in which the bellows is partially compressed, such that thetubular gate or wedge has just been sealed against the valve seat.

FIG. 12 is a cross-sectional view of a portion of a standard edge-weldedbellows featuring spherical weld beads, shown in an extended position.

FIG. 13 is a cross-sectional view of the portion of the standardedge-welded bellows of FIG. 12 shown in a nested position.

FIG. 14 is a cross-sectional view of a portion of an edge-welded bellowsfeaturing rectangular weld beads, shown in an extended position.

FIG. 15 is a cross-sectional view of a portion of the edge-weldedbellows of FIG. 14, shown in a nested position.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, the invention is intended to cover alternatives,modifications and equivalents, which may be included within the spiritand scope of the invention as defined by the claims. Furthermore, in thedetailed description of the present invention, several specific detailsare set forth in order to provide a thorough understanding of thepresent invention. However, one of ordinary skill in the art willappreciate that the present invention may be practiced with or withoutthese specific details. Thus, while the invention is susceptible toembodiment in many different forms, the subsequent description of thepresent disclosure should be considered as an exemplification of theprinciples of the invention, and is not intended to limit the inventionto the embodiments so illustrated.

FIG. 1 depicts one type of gas turbine engine 20. As is known in thisfield, gas turbine engines may include a fan section 30, which moves airand rotates about central axis 40. As fan 41 rotates within fan section30, air is pushed towards the rear of the engine 42 along central axis40, successively into each of compressor section 50, combustor section60, and turbine section 70, respectively, each of which is also centeredalong central axis 40. Exemplary bleed valve 80 is shown positioned oncompressor casing 51 of compressor section 50. Gas turbine engine 20 mayincorporate numerous bleed valves 80 in various locations. While much ofthe discussion below assumes that bleed valve 80 is mounted oncompressor section 50 of gas turbine engine 20, the various embodimentsof bleed valve 80 discussed below may likewise be positioned in any ofthe other sections of gas turbine engine 20, including on combustorsection 60 and turbine section 70. FIG. 1 schematically shows only thekey components of a gas turbine engine, and it will be understood thatnumerous other components of such an engine are not shown for the sakeof simplicity. Further, while one of skill in the art would recognizethat gas turbine engine 20, shown in FIG. 1, is one particular type ofthe many gas turbine engines known in the field, it should be understoodthat the present invention extends to other types of gas turbineengines.

FIGS. 2A-2B depict an elevated cross-sectional view of an exemplarypreferred embodiment of a bleed valve according to the presentinvention, namely, bleed valve 100. Bleed valve 100 includeshigh-pressure cavity 110 and valve housing 120, which are rigidlycoupled together so as to create a hermetically sealed interior volumewithin high-pressure cavity 110. In the embodiment shown in FIGS. 2A-2B,high-pressure cavity 110 is coupled to valve housing 120 via fastenerelements 116, 117, which in this case are bolts 116, 117. However, oneof ordinary skill in the art would appreciate that high-pressure cavity110 and valve housing 120 may likewise be rigidly coupled together in avariety of ways, including through adhesives or welding, or they may beformed as a single, integrated piece.

In FIGS. 2A-2B, the first end 112 of high-pressure cavity 110 ispositioned at the top of high-pressure cavity 110, whereas secondopposite end 114 of high-pressure cavity 110 is rigidly coupled to firstor top end 122 of valve housing 120. Within high-pressure cavity 110 ispositioned bellows 140, which has its own first, top end 142 and second,bottom end 144. Second end 144 of bellows 140 is fixed, and is rigidlycoupled and hermetically sealed to either (a) the second end 114 ofhigh-pressure cavity 110, or (b) the first, top end 122 of valve housing120. By contrast, first end 142 of bellows 140 is movable, and isconfigured (within the orientation of FIGS. 2A-2B) to reciprocateupwardly and downwardly within high-pressure cavity 110. In thisembodiment, first end 142 of bellows 140 is rigidly coupled andhermetically sealed to end cap 130, for joint reciprocating movementwithin high-pressure cavity therewith. Bellows 140 further comprisesinterior surface 145, exterior surface 146 and interior volume 148.

As also shown in FIGS. 2A-2B, bleed valve 100 may further comprise aplurality of sealing elements configured to hermetically seal interiorvolume 148 of bellows 140. As one example of such a sealing element,first end 142 of bellows 140 may be welded, such as laser-welded, to endcap 130 to hermetically seal first end 142 of bellows 140. As anotherexample, second end 144 of bellows 140 may be welded, such aslaser-welded, to either second end 114 of high-pressure cavity 110, orto first end 122 of valve housing 120, to likewise hermetically sealsecond end 144 of bellows 140. Another sealing element may compriseannular sealing ring 125, which is positioned between second end 114 ofhigh-pressure cavity 110 and first end 122 of valve housing 120.

Bellows 140, and specifically first end 142 of bellows 140, is operablycoupled to system poppet 150 by way of shaft 152 and shaft extension154. Beyond the end of shaft 152 is positioned the sealing portion 151of system poppet 150, which cooperates with valve seat 160 to preventthe passage of a fluid (typically, air) through valve seat 160, wherethe fluid can exit through apertures 127, 128 to the outside atmosphere.First end 153 of shaft extension 154 may be rigidly coupled andhermetically sealed to end cap 130 by welding, such as by laser welding.Such welded joints between end cap 130, first end 142 of bellows 140,and shaft extension 154 (or integrated shaft 252, discussed belowrelative to FIG. 6) and shaft end 153 seal end cap 130, relative tobellows 140.

However, it will be appreciated that there are a variety ofconfigurations in which first end 142 of bellows 140 could be coupled,directly or indirectly, to system poppet 150. For example, shaft 152 maysimply be formed as a single integrated piece with system poppet 150, inwhich shaft 152 extends up to first end 142 of bellows 140. Thatconfiguration can be seen in FIG. 6, in which system poppet 250 iscoupled to first end 242 of bellows 240 via integrated shaft 252.

As shown in FIGS. 2A-2B, 3 and 4, system poppet 150 is configured tocooperate with valve seat 160, which is positioned in second end 124 ofvalve housing 120. In view of the rigid coupling of system poppet 150,indirectly, to first end 142 of bellows 140, the combination of bellows140 and system poppet 150 serves as a reciprocating valve configured toseal valve seat 160, based on the pressures exerted both upon theexterior of bellows, as well as from within the interior of bellows 140.Specifically, in bleed valve 100's open configuration, as shown in FIGS.2A-2B, interior volume 148 of bellows 140 is pressurized with asignificant amount of fluid, via servo air port 180, an amount that issufficient to exert pressure onto interior surface 145 of bellows 140,forcing bellows 140 into its expanded position. However, high-pressurecavity 110 of bleed valve 100 is likewise configured to describe aninterior volume 118, which can be pressurized by another fluid via airport(s) 170, to thereby exert a force about exterior surface 146 ofbellows 140, towards forcing bellows 140 into its compressed position(shown in FIGS. 3-4).

Pressurizing bellows 140 and high-pressure cavity 110, to thereby openor close bleed valve 100, respectively, are actions that may becontrolled or performed by a pilot of the aircraft, by an onboard flightcomputer, or by other means. The actions can be specifically carried outvia one or more air ports for carrying and injecting air or otherfluids. For example, high-pressure cavity 110 may be pressurized byinjecting air or another fluid via one or more cavity air ports, such asair port 170. Doing so will compress bellows 140, thereby moving firstend 142 of bellows 140 towards second end 114 of high-pressure cavity110, and pushing system poppet 150 downwardly, and sealing second end151 of shaft 152 against valve seat 160, thus closing bleed valve 100.

By contrast, bellows 140 may be pressurized to expand, by injecting airor another fluid via servo air port 180. As explained further below,doing so will allow bellows 140 to expand, in part due to the springbias force inherent in bellows 140, as well as due to any additionalpressure introduced by way of air or other fluids entering into bellows140 from servo air port 180. As part of the expansion of bellows 140,first end 142 of bellows 140 will move towards first end 112 ofhigh-pressure cavity 110, thus pushing system poppet 150 upwardly, andopening bleed valve 100. While the drawings show cavity air port 170 andservo air port 180 as being encased within valve housing 120, one ofskill in the art would understand that the air ports 170, 180 may beconfigured to be separate from valve housing 120.

FIG. 2B of the drawings shows bleed valve 100 installed on compressorcasing 51 (see FIG. 1), such that air from within compressor section 50of jet engine 20 can enter a bleed valve, such as bleed valve 100, viavalve seat 160, to enable the escape of such air or gas to the outsideatmosphere, via apertures 127, 128 in valve housing 120.

FIG. 3 of the drawings shows bleed valve 100 in its initially closedconfiguration, in which second end 151 of system poppet 150 has justmade contact with, and has been sealed against, valve seat 160. This wasaccomplished by injecting air or another fluid into the interior volume118 of high-pressure cavity 110 via cavity air port(s) 170, thuscompressing bellows 140. Notably, however, in the configuration shown inFIG. 3, bellows 140 is, in part, compressed, but it is not fullycompressed into a nested position. As will be described relative to FIG.4, the ability of bellows 140 to fully compress into a substantiallynested position provides additional advantages over conventional bleedvalves.

In the closed position of bleed valve 100, as shown in FIGS. 3-4, whenbleed valve 100 is positioned on the compressor section 50 of a jetengine 20, bleed valve 100 is configured to be positioned such thatpressurized gases flowing through the compressor section 50 areprevented from flowing through valve seat 160. As also seen in FIGS.3-4, bellows 140 is configured to be in a compressed state when bleedvalve 100 is closed.

Bleed valves 100, 200 (described below relative to FIGS. 2-6) and 300(described below relative to FIGS. 7-11) include several features thatare designed to reduce the load borne by the valves—and that each renderthe present bleed valve “self-compensating,” i.e., that ensure thatbleed valves 100, 200, and 300 stay closed when they are intended to beclosed and stay open when they are intended to be open. First, as shownin the orientation of FIG. 3, it can be seen that the mean effectivearea of bellows 140, MEA_(B), is greater than the mean effective area ofsecond end 151 of system poppet 150, where it seals against valve seat160, MEA_(V) (i.e., MEA_(B)>MEA_(V)). Many conventional designs use anopposite configuration, in which the mean effective area of the systempoppet is greater than the mean effective area of the bellows. In thesecases, when such a conventional valve is positioned in its closed state,the system poppet is exposed to significant amounts of pressure from thecompressor section of the engine, which can generate significant amountsof force against the system poppet and sealing surface, which forcecarries through to the valve body and shaft. Such approaches typicallyrequire the system poppet, valve seat, shaft and valve body to each bestrong enough to withstand the significant degrees of force generated bythe compressor, thereby requiring such valves to add additionalmaterials, at a higher cost, in order to avoid failure of the valve.Maintaining the mean effective area of bellows 140 greater than the meaneffective area of system poppet 150 minimizes the total amount of forcethat valve 100 must be able to withstand, thereby reducing the forces onthe valves, resulting in significantly lower valve failure rate. In thepresent invention, each of bleed valves 100, 200, and 300 isself-compensating, and is more likely to stay closed, when intended.

Second, bleed valve 100, 200 and 300 are self-compensating because, asexemplified by FIG. 3, system poppet 150 is configured to movedownwardly towards valve seat 160, the same downward direction in whichbellows 140 is compressing, and in which shaft 152 is moving. In thisway, any failure of bellows 140, such as failure of any sealing elementsof the bellows, will cause valve 100 to move into its closedconfiguration. A configuration in which bellows 140 compresses in thesame high-pressure direction in which system poppet 150 closes and sealsagainst valve seat 160, again makes it more likely that a net positiveforce will push system poppet 150 into a position to seal against valveseat 160. This same feature of self-compensation applies to the closureof bleed valve 300 in FIG. 8. More specifically, bleed valve 300 isconfigured in such a way that the bellows will compress in the samedirection in which the valve closes.

The present invention further contemplates the selection and use of aspecific type of bellows, or that the amount of compression (or“precompression”) in bellows 140 may be “factory set” or adjusted, toensure that the operating pressure differentials are maintained withinspecified and/or optimized performance limits. One way that this isachieved is by adjusting the position of end cap 130 relative to thesealing end 151 of system poppet 150. In other words, setting aprescribed distance between end cap 130 and sealing end 151 of systempoppet 150 can be utilized to regulate or define an intended spring biasinherent in bellows 140, thus bleed valve 100 to operate withinpreferred operating parameters.

FIG. 4 depicts bleed valve 100 in its fully closed configuration, whichis achieved after a partially closed configuration, through theinjection of additional air or another fluid into the interior volume118 of high-pressure cavity 110 via cavity air port(s) 170, therebycompressing bellows 140 to its fully compressed, fully nested, position.Compressing bellows 140 to its nested position provides significantadvantages over conventional bleed valves. Specifically, since bleedvalve 100 is intended to be used in an environment with significantamounts of vibration (e.g., on the compressor casing 51 of a gas turbineengine 20), it is advantageous for bellows 140 to be fully compressed toits nested condition in order to dampen the bellows. An undampedbellows, such as that shown in FIGS. 2A-2B and 3, will be subjected tosignificant vibration. As noted above, bleed valve 100 will occupy itsclosed position for most of its operating life, and may be opened solelyfor startup of the engine, and also potentially for taxiing, transientevents, take-off and landing. Since bellows 140 is in its nestedposition when bleed valve 100 is fully closed, and since bleed valve 100will spend most of its operating life in that fully closed position, thelifespan of bellows 140—and, thus, of bleed valve 100—will besignificantly lengthened by the fact that bellows 140 is nested, anddampened during most of its operation. The significant degree ofvibration to which bellows 140 and bleed valve 100 are exposed and mustendure over their respective life spans could greatly enhance the riskof catastrophic failure of bleed valve 100 and/or bellows 140, ifbellows 140 was in any of its uncompressed, un-nested states during suchenduring vibration.

In contrast, many conventional bleed valves utilize designs in whicheither a bellows or an energized spring is positioned into an expandedstate when the valve is closed. Since the valve will be closed duringthe vast majority of its operating life, the expanded bellows and/orsprings in such valves will be constantly subjected to significantamounts of vibration, thus increasing the risk that the bellows and/orsprings in such valves will break or fail. The design disclosed hereinimproves upon those conventional bleed valves by minimizing such risk ofcatastrophic bellows failure, through the elimination of risksassociated with strong vibrations affecting bellows and/or springs intheir expanded states. By designing bleed valve 100 to incorporatebellows 140, which is fully compressed to its nested state when bleedvalve 100 is closed (and, thus, for most of the operating life of bleedvalve 100), the design disclosed herein is believed to substantiallyincrease the life span of the valve.

FIG. 5 of the drawings depicts bleed valve 100 in its open state, afterit has been redirected to its open orientation. The valve is opened byinjecting air or another fluid through servo air port 180, and directlyinto bellows 140. As additional air or fluid is injected into bellows140, that air or fluid exerts a pressure against the internal surface145 of bellows 140. While the spring force of bellows 140 serves toessentially open the valve, the servo air pressure will act to furtherreduce the pressure differential across bellows 140, to expand bellows140 with the inherent spring bias of bellows 140. The servo air pressuremay meet or exceed the bellows' external pressure, but exceeding theexternal pressure is not required to open the valve. Simply put, bellows140 may be configured to utilize its own inherent spring bias, such thatinjecting air or fluid into bellows 140 via servo air port 180 reducesthe pressure differential across bellows 140, such that bellows 140 mayexpand into its open position. When the pressure against internalsurface 145 of bellows 140 meets or exceeds the amount of pressureexerted against external surface 146 of bellows 140 by the air or fluidwithin internal volume 118 of high-pressure cavity 110, the inherentspring bias of bellows 140 may enable bellows 140 to expand until itreaches its fully expanded state. In that state, an additional backupsealing element may be utilized to ensure that no air or other fluidescapes from within interior volume 148 of bellows 140. Specifically,when valve 100 is in its open position, posterior surface 151′ of systempoppet 150 may form an annular metal-to-metal contact seal 123 at itsupper end, sealing posterior surface 151′ against interior surface 121of valve housing 120.

FIG. 6 of the drawings shows a second embodiment of a bleed valveaccording to the present disclosure, in the form of bleed valve 200.Bleed valve 200 differs from bleed valve 100 in a few ways. Mostnotably, bleed valve 200 incorporates system poppet 250 in which shaft252, which connects first end 253 of system poppet 250 and movable endcap 230 of bellows 240 to the second end 251 of system poppet 250,comprises a single, solid, integrated assembly 252, without any internalcavities therewithin.

The structure of FIG. 6 is in contrast with shaft 152 of system poppet150, shown in FIGS. 2A-2B, which incorporates internal shaft cavity 155,in which spring 156 is positioned. In bleed valve 100, internal shaftcavity 155 and spring 156, together with shaft extension 154,collectively comprise one example design for an “over travel” element,which enables bellows 140 to fully nest into a solid, cylindrical,self-supporting stack after system poppet 150 has fully seated againstvalve seat 160. This “over travel” element limits the amount of stressthat may be applied onto valve seat 160 and system poppet 150 (and, inturn, the amount of stress that may be applied onto other elements ofbleed valve 100, such as bellows 140 or high-pressure cavity 110), whensignificant stage pressures are generated in compressor section 50 ofgas turbine engine 20. It is expected that stage pressures may reachgreater than 400 psi, and allowing bellows 140 to fully compress intoits nested position (shown in FIG. 4) well below that 400 psi limitserves to minimize the total forces that may be applied across bleedvalve 100. This, in turn, allows for the selection of materials thatweigh less, and that are less costly, thus improving the functionalityof bleed valve 100 without adding significant weight or cost.

A second, alternative design for the “over travel” element is shown inFIG. 6. This embodiment does not include the use of an internal shaftcavity, a spring, or a shaft extension. Instead, bleed valve 200includes bellows 240, which incorporates certain flexure elements 249welded to the first end 242 of bellows 240. Flexure elements 249 aredepicted in FIG. 6 as comprising curved portions welded to first end 242of bellows 240. One of skill in the art would understand that the exactcurvatures and locations depicted may be varied without departing fromthe scope of the invention. Flexure elements 249 serve to enable bellows240 to fully nest into a substantially solid condition after systempoppet 250 has fully seated against valve seat 260, thereby limiting theamount of stress that bleed valve 200 may endure.

FIG. 6 depicts yet another design feature that may be useful inexpanding the life span of bleed valve 200 in many embodiments. It isexpected that contaminants, including sand, rocks, bones, and the liningof engine casings, among others, may impinge upon bleed valve 200, andspecifically may be introduced into high-pressure cavity 210, valvehousing 220, or other components of bleed valve 200. Without anyprotection from such contaminant particles, bleed valve 200 could beseverely damaged, or could fail. Thus, bleed valve 200 includes anintegrated filtration unit 275 intended to prevent contaminants fromentering high-pressure cavity 210 and causing damage to bellows 240 orother sensitive portions of bleed valve 200. Integrated filtration unit275 may comprise one or more filter discs that are positioned betweenvalve housing 220 and high-pressure cavity 210, within cavity air port270. While integrated filtration unit 275 is shown in one particularlocation, other or additional integrated filtration units may beincluded in other locations, including, potentially, within servo airport 280.

FIGS. 7-9 depict an elevated cross-sectional view of a third example ofa preferred embodiment of a bleed valve according to the presentinvention, namely, bleed valve 300. As set forth below, bleed valve 300operates according to the above-described principles of bleed valves 100and 200, in which the bellows compresses in the same direction in whichthe valve closes. However, while bleed valves 100 and 200 utilize twohousing elements, namely, high-pressure cavity 110 and valve housing120, which are rigidly coupled together, bleed valve 300 may utilizethree housing elements, namely, high-pressure cavity 310, valve terminal320 and cap 370. As shown in FIGS. 7-9, high-pressure cavity 310 servesas a base upon which valve terminal 320 is positioned and affixed, withcap 370 serving as the third valve housing element. Similar to bleedvalves 100 and 200, high-pressure cavity 310 is affixed to valveterminal 320 in such a way as to create a hermetically sealed interiorvolume within high-pressure cavity 310, in which bellows 340 is located.As discussed above, one of ordinary skill in the art would appreciatethat high-pressure cavity 310 and valve housing 320 may be rigidlycoupled together in a variety of ways, including through fasteners,adhesives or welding, or they may be formed as a single, integratedpiece.

In FIGS. 7-9, and in contrast with bleed valve 100, in which the firstend 112 of high-pressure cavity 110 is positioned at the top ofhigh-pressure cavity 110, the first end 312 of high-pressure cavity 310is positioned at the bottom of high-pressure cavity 310. Further, secondopposite end 314 of high-pressure cavity 310 is rigidly coupled to firstor bottom end 322 of valve terminal 320. In addition, second oppositeend 324 of valve terminal 320 is rigidly coupled to first or bottom end372 of cap 370. Within high-pressure cavity 310 is positioned bellows340, which has its own first, bottom end 342 and second, top end 344.Second end 344 of bellows 340 is fixed (e.g., by welding) and is rigidlycoupled and hermetically sealed to either (a) the second end 314 ofhigh-pressure cavity 310, or (b) the first, bottom end 322 of valveterminal 320. By contrast, first bottom end 342 of bellows 340 ismovable, and is configured (within the orientation of FIGS. 7-9) toreciprocate upwardly and downwardly within high-pressure cavity 310. Inthis embodiment also, first end 342 of bellows 340 is rigidly coupledand hermetically sealed (e.g., by welding) to sealing tube 350, whichsealing tube 350 jointly reciprocates together with the first, bottomend 342 of bellows 340, within high-pressure cavity 310. Bellows 340further comprises interior surface 345, exterior surface 346 andinterior volume 348.

In bleed valve 300's open configuration, as shown in FIG. 7, interiorvolume 348 of bellows 340 may be pressurized with a desired amount offluid, via servo air port 380. The bellows fluid is sufficient to exertpressure onto interior surface 345 of bellows 340, forcing bellows 340into its expanded position. In addition, as explained above in Paragraph[0090], bellows 340 also has an inherent spring bias. Servo air port 380may be formed integrally to terminal 320, and may be configured toinject pressurized fluid directly into and within bellows 340. Theinjection of pressurized fluid by the servo air port serves to furtherreduce the pressure differential across bellows 340, with thepressurized fluid exerting a force against interior surface 345 ofbellows 340, thereby expanding bellows 340. The pressure of the fluidinjected by the servo air port may meet or exceed the external pressureon bellows 340, but exceeding the external pressure is not required toopen the valve. Rather, bellows 340 may be configured to utilize its owninherent spring bias, such that injecting air or fluid into bellows 340via servo air port 380 reduces the pressure differential across bellows340, such that bellows 340 may expand into its open position. The servoair port may be controlled by the pilot, by an onboard computer, or byother means to command the valve open when needed.

High-pressure cavity 310 is also configured to describe an interiorvolume 318, which may be pressurized by another fluid via air port(s)(not shown in FIGS. 7-9), to thereby exert a force about exteriorsurface 346 of bellows 340, towards forcing bellows 340 into itscompressed position. As a result, there are two “cavities” that,depending on the pressure within each cavity, may cause the valve toopen or close. The first cavity is high-pressure cavity 310, which maybe defined as interior volume 318, being bounded by exterior surface 346of bellows 340, the bottom-facing surface 321 of terminal 320, and theinterior surface 311 of base or high-pressure cavity 310. The second“cavity” is interior volume 348 of bellows 340, which interior volume348 is bounded by the interior surface 345 of bellows 340, and by theoutside diameter of sealing tube 350 and the bottom facing surface 321of terminal 320.

As shown in FIGS. 7 and 8, in order to prevent excessive vibration fromdegrading the life of valve 300 when the valve is in the open condition,damping strip 315 may be used to surround outside diameter 316 ofbellows 340, with damping strip 315 being configured in such a way as tomake continuous and deliberate contact with outside diameter 316 ofbellows 340 along the entire length of bellows 340. The base orhigh-pressure cavity 310 may include structural indentation 315A orother feature that serves to hold damping strip 315 in place, or inwhich damping strip 315 is embedded. Bellows 340 is not physicallyconnected to any portion of damping strip 315, such that the strip 315does not hinder or prevent bellows 340 from reciprocating between itsopen and closed positions.

Bellows 340, and specifically first, bottom end 342 of bellows 340, isoperably coupled to sealing tube 350, partly by way of attachment totube base 352. As noted above, this operable coupling of bellows 340 andsealing tube 350 may be accomplished by welding, laser welding, or anyother known means of hermetic sealing affixation. At its opposite,second end 354, the top 351 of sealing tube 350 is configured tocooperate with valve seat 360 to prevent fluid (e.g., air) from passingthrough valve seat 360, where the fluid can exit through apertures 327,328 (see FIGS. 10-11) to the outside atmosphere.

As shown in FIGS. 7-11, sealing tube 350 is configured to cooperate withvalve seat 360, which, in this embodiment, is a cylindrical featurelocated on the underside 371 of cap 370. As one of skill in the artwould appreciate, the feature being cylindrical is merely one designchoice, and the invention is not intended to be limited to the shape ofvalve seat 360 as requiring a cylindrical feature. Since sealing tube350 is rigidly coupled to first end 342 of bellows 340, the combinedassembly of bellows 340 and sealing tube 350 serves as a reciprocatingvalve 356 that is configured to seal valve seat 360, based on thepressures exerted both upon the exterior of bellows 340, as well aswithin the interior of bellows 340. Specifically, as discussed above, toorient bleed valve 300 in its open configuration, as shown in FIG. 7,interior volume 348 of bellows 340 is pressurized with fluid that issufficient to exert pressure onto interior surface 345 of bellows 340,forcing bellows 340 into its expanded position. As noted above inParagraph [0090] relative to bellows 140 and in Paragraph [0097]relative to bellows 340, bellows 340 has its own inherent spring bias,and the pressurized fluid injected by servo air port 380 serves toreduce the pressure differential across bellows 340, such that the valveopens and the bellows begins to expand when the servo air pressure meetsor exceeds the bellows external pressure, but, again, exceeding theexternal pressure is not required to open the valve. Thus, bellows 340may be configured to use its own inherent spring bias in such a way thatinjecting air or fluid into bellows 340 reduces the pressuredifferential, thereby allowing bellows 340 to expand. By contrast, wheninterior volume 318 is pressurized by another fluid via air ports (notshown), a force is exerted about exterior surface 346 of bellows 340,thus forcing bellows 340 into its compressed position (initially shownin FIG. 8). FIG. 9 shows bellows 340 being further fully compressed intoits nested position, to thereby provide the significant advantage offurther dampening the bellows by way of its nesting.

While FIGS. 7-9 show the structure and operation of bleed valve 300, theperspective views of FIGS. 10-11 further illustrate the flow path offluids through bleed valve 300. As shown in FIGS. 10A-10B, when bleedvalve 300 is in its open position, bellows 340 is expanded, and sealingtube 350 is recessed downwardly within terminal 320. As shown by thedirection of the arrows in FIGS. 10A-10B, with valve 300 being open, airor other fluids are allowed to flow up the middle of tube 350, exitingthrough the second end 354 of tube 350, and into the radial volume 375,bounded within the interior surface of cap 370 and terminal 320. Testingand analysis of prototypes of bleed valve 300 have shown that theconfiguration of this fluid flow path results in a highly favorabledischarge coefficient, one that is greater than 0.90.

FIGS. 10-11 importantly depict perforated air filter 319 affixed to thebottom side of base 310. Air filter 319 may be used to filter the fluidsentering bleed valve 300, and may prevent the introduction of foreignobjects and debris from coming into contact with external surface 346 ofbellows 340. Further, while air filter 319 is shown in FIGS. 10-11 asbeing affixed to the bottom of base 310, but not serving to filterfluids traveling upwardly through tube 350, one of skill in the artwould understand that filter 319 may also be extended to cover thebottom of tube 350, such that fluids flowing upwardly through tube 350can be routed through air filter 319. As the amount of fluid flowingthrough valve 300 increases, back pressure is generated in the center oftube 350 and in high-pressure cavity 310. The pressurized fluid exerts apressure on the exterior surface 346 of bellows 340, thereby compressingbellows 340. Notably, bellows 340 is a flexible member that may bepre-compressed at installation, such that valve 300 only begins to moveonce the pressure in the high-pressure cavity 310 exceeds the pressureestablished within bellows 340 by a desired pressure differential.

As bellows 340 is compressed, the first, movable end 342 of bellows 340moves tube 350 upwardly, thereby reducing the exit area of the valve. Asthe back pressure reaches a sufficient magnitude so as to cause bellows340 to compress by a desired amount, tube 350 extends towards, andcooperates with, valve seat 360, the cylindrical feature located on theunderside 371 of cap 370. Once tube 350 moves upwardly and makes contactwith valve seat 360, the fluid that is flowing upwardly within tube 350is prevented from flowing further, by virtue of the radial seal that isformed between either (a) the inside diameter of tube 350 and “lip” oroutside diameter 361 of cylindrical feature 360 of cap 370, or (b) theoutside diameter of tube 350 and an inside diameter (not shown) ofcylindrical feature 360 of cap 370. With bellows 340 continuing tocompress, tube 350 continues to move upwardly to fully seal againstvalve seat 360, causing valve 300 to close to, in turn, prevent fluidfrom exiting the valve. As one of skill in the art would appreciate,there is little to no difference between the operation of valve 300regardless of whether a designer chooses to implement option (a) or (b)of this paragraph, both of which may be hereafter referred to as thevalve's “radial seal arrangements.”

The radial seal arrangements allow valve 300 to continue closing untilbellows 340 is fully nested, as shown in FIG. 9, thus self-compensatingfor any tolerance stacks or thermal growth across the valve. Further, asdiscussed in more detail below relative to FIGS. 12-15, bellows 340 mayhave rectangular weld beads, such that when bellows 340 is compressedinto its fully nested position, the rectangular weld beads stack on topof one another to form a solid, self-supporting cylindrical stack.

As shown in FIGS. 12 and 13, a standard edge-welded bellows (not fullyshown) consists of bellow plates 1200 having circular weld beads 1210 ateach welding location. When the bellows is extended, as shown in FIG.12, circular weld beads 1200 function normally. However, when thebellows is fully compressed under a relatively high pressure on theorder of 100 psi, circular weld beads 1210 will be compacted together.Due to their circular shape, the arcs 1214 of each adjacent weld beadcould shear, creating an imperfect alignment, resulting in the displacedconfiguration shown in FIG. 13. Unlimited shearing can lead to failureof the bellows, which could result in a catastrophic failure of a bleedvalve.

One method for increasing the overall strength and integrity of anedge-welded bellows is to weld the plates together such that the weldbeads are substantially rectangular in shape. In FIG. 14, theedge-welded bellows (not fully shown) consists of bellows plates 1400having rectangular, internal weld beads 1410. When such a bellows iscompressed into its fully nested position, as shown in FIG. 4 and inFIG. 9, rectangular weld beads 1410 stack neatly, and efficiently, ontop of one another. Thus, when nested, a bellows having rectangular weldbeads 1410 forms a solid, self-supporting cylindrical stack, capable ofwithstanding much higher pressures than the standard bellows shown inFIGS. 12 and 13. Such bellows having rectangular weld beads areavailable from Senior Metal Bellows corporation of Sharon, Mass., andare sold under the trademark HIPRES®, which trademark is owned by theassignee of the present application.

The foregoing description and drawings merely explain and illustrate theinvention. However, the invention is not intended to be limited to anyone particular embodiment or combination of elements shown in connectionwith any particular drawing, as those skilled in the art who have thedisclosure before them will be able to make modifications and variationstherein without departing from the scope of the invention.

Further, the foregoing description presents a best mode contemplated forcarrying out the present embodiments, and of the manner and process ofpracticing them, in such full, clear, concise, and exact terms as toenable any person skilled in the art to which they pertain to practicethese embodiments. The present embodiments are susceptible tomodifications and alternate constructions from those discussed above,which modifications and alternate constructions are equivalent to thosediscussed above. Consequently, the present invention is not limited tothe particular embodiments disclosed. On the contrary, the presentinvention covers all modifications and alternate constructions comingwithin the spirit and scope of the present disclosure, and within thescope of the claims.

We claim:
 1. A bleed valve for use in a gas turbine engine of anaircraft, the bleed valve comprising: a high-pressure cavity having aninterior surface, an interior volume, a first end and a second endopposite said first end; a valve terminal having an exterior surface, afirst end, a second end opposite said first end, and one or moreapertures, said second end of said high-pressure cavity being coupled tosaid first end of said valve terminal; a cap having a first end and oneor more apertures, said second end of said valve terminal being coupledto said first end of said cap; a bellows for alternatively capturing andreleasing one or more pressurized fluids, said bellows having aninterior surface, an interior volume, an exterior surface, a firstmovable end and a second fixed end opposite said first movable end, saidsecond fixed end of said bellows being operably coupled to one of saidinterior surface of said high-pressure cavity and said exterior surfaceof said valve terminal, at a position substantially adjacent the secondend of said high-pressure cavity; a sealing tube having a first end anda second end opposite said first end, said first end of said sealingtube being operably coupled to the first movable end of said bellows,said second end of said sealing tube configured to cooperate with andseal a valve seat located on the cap, said bellows being configured toexpand and compress based upon the injection of one or more pressurizedfluids into the bellows and surrounding the bellows, respectively, saidbleed valve being configured to be self-compensating, such that when thebleed valve is in its closed configuration, said sealing tube isoriented to be sealed against the valve seat, with the bellows in itscompressed position.
 2. The bleed valve of claim 1, in which theinjection of said one or more pressurized fluids is collectivelyconfigured to be controllable by one of (a) a pilot of said aircraft,(b) an onboard flight computer, and (c) by other means.
 3. The bleedvalve of claim 1, in which a servo air port is encased within said valveterminal.
 4. The bleed valve of claim 1, in which said bellows hasrectangular weld beads, such that when said bellows is compressed intoits fully nested position, said rectangular weld beads stack on top ofone another to form a solid, self-supporting cylindrical stack.
 5. Thebleed valve of claim 1, in which the mean effective area of said bellowsis larger than the mean effective area of said sealing tube.
 6. Thebleed valve of claim 1, in which the first movable end of the bellows isrigidly coupled and hermetically sealed to said sealing tube.
 7. Thebleed valve of claim 6, in which the rigid coupling and hermetic sealingof said first movable end of the bellows and said sealing tube isaccomplished through welding.
 8. The bleed valve of claim 7, in whichthe rigid coupling and hermetic sealing of said first movable end of thebellows and said sealing tube is accomplished through laser welding. 9.The bleed valve of claim 1, in which the bleed valve is configured to bepositioned within the compressor stage of said gas turbine engine. 10.The bleed valve of claim 1, in which the bleed valve is configured to bepositioned within the turbine stage of said gas turbine engine.
 11. Thebleed valve of claim 1, in which the bleed valve is configured to bepositioned within the combustor stage of said gas turbine engine. 12.The bleed valve of claim 9, in which the bleed valve is configured, whenin its closed position in which said sealing tube is sealed against saidvalve seat, to be positioned such that a pressurized gas flowing throughsaid compressor stage of said gas turbine engine is prevented fromflowing through said valve seat.
 13. The bleed valve of claim 1, inwhich the bellows is configured to be capable of further compression toa nested state when the valve is closed.
 14. The bleed valve of claim 1,in which the bleed valve further comprises an integrated filtration unitto prevent one or more contaminants from entering the high-pressurecavity.
 15. The bleed valve of claim 14, in which the integratedfiltration unit comprises an air filter positioned at the bottom of thehigh-pressure cavity.